1. Field of the Invention
This invention relates to a video tape recorder (VTR), and more particularly to a multi-channel VTR which records a video signal separated into N channel components (N being a number larger than two) on a magnetic tape and then reproduces the recorded signal.
2. Description of the Prior Art
Conventional 2-channel VTRs are widely used for broadcasting and recording video signals on a magnetic tape via two pairs of rotary heads in such a manner that a frequency modulated (FM) luminance signal Y and a FM chrominance signal C are recorded on separate tracks which are arranged alternately in the order of Y, C, Y, C, Y, C,--. The FM chrominance signal is a signal which is obtained by time-base-compression-multiplexing two chrominance difference signals and frequency-modulating the multiplexed signal, or a signal which is obtained by frequency modulating two chrominance difference signals with different carrier frequencies and mixing the frequency-modulated signals (so-called frequency-division-multiplexed signal), or a signal which is obtained by frequency-modulating so-called line sequential chrominance difference signals which appear alternately at a cycle of one horizontal scanning period. These are disclosed in Japanese Laid-Open patent application (Kokai) Nos. 59-4279, 59-34785, 58-131885, 59-104886 and 59-104887. Each pair of heads are disposed so as to be 180 degrees apart from each other on a circumference of a rotary cylinder. One head of each pair is disposed adjacent to one head of the other pair. A typical conventional 2-channel VTR is shown in "A 1/2 INCH METAL-CASSETE VTR SYSTEM" by S. Matsuda et al., Technical Report of the Institute of Television Engineers of Japan, Vol. 9, No. 2 (May, 1985), pp. 19-24.
Although the conventional 2-channel VTRs can provide high quality video signals, they have the following disadvantages.
The conventional 2-channel VTRs operate in only one fixed operation mode, i.e., standard mode, but cannot operate in special operation modes such as a long play mode. If they were required to operate in an additional operation mode, two additional pairs of heads would have to be provided on the rotary cylinder, which would be very difficult or almost impossible.
Furthermore, the conventional 2-channel VTRs, when recording, provide a guard band between two adjacent signal tracks on the magnetic tape for eliminating crosstalk between the signals recorded on the adjacent signal tracks. This is disadvantageous for the purpose of increasing recording density.
Furthermore, since two heads are disposed adjacent to each other, production and adjustment of the head system are very difficult, and a shield plate must be provided between two adjacent heads for eliminating crosstalk between the two adjacent heads. As the result, the head system of the conventional 2-channel VTRs is too expensive to be used for home use. This is the main reason that the 2-channel VTRs have been used only for broadcasting.
Furthermore, the signal quality of the reproduced signal is too poor to be used even as a home use VTR when the bandwidth of the recording signal is wider, or when the required SN ratio is higher in the newer systems such as EDTV, HDTV.